Exploring The Incredible Ability To Play Dead And The Animals That Have Mastered The Art
Animals have evolved with a wide variety of skills to both evade predators, or to trick their prey. There are those that can camouflage themselves against their surroundings, or those like porcupines and hedgehogs that have a body covered in spines to deter any would be attacker. Some have amazing speed or spray out offensive odour.
But there are some, that don’t have any of these skills. That can’t outrun their threat, or produce a smell or curl up into a protective, spikey ball. So what do you do when you are vulnerable and your back us up against the wall? You play dead!
We take a look at a range of animals that play dead, or more correctly, enter a type of comatose state called Thanatosis. There are animals that do this in a range of different ways, and for different reasons. Let’s take a look!
What Is Apparent Death, aka Thanatosis?
When an animal feigns death, it’s not usually a conscious choice, but rather an instinctive reaction to a stimulus. It is not only a response to stimulus from an approaching threat, but can also be used by some animals to trick prey into getting close enough to snatch. In either case, the animal goes into a state of apparent death known as Thanatosis, or ‘Tonic Immobility’.
In most cases, the event occurs late in the process of being approached by a predator, or on some cases, immediately after a predator has made physical contact.
When an animal enters a state of thanatosis, they become temporarily paralyzed and unresponsive to the external environment. You could poke them with a stick and they won’t respond. In some cases, they may remain conscious while the state is in effect, but with each animal there can be a variety of different attributional effects that take place alongside the apparent death.
Post-Contact Immobility is where thanatosis takes place very late in the encounter with a predator, after they have made initial contact. It is seen in this phase, as a secondary defence strategy, imposed as a last chance to deter a predator from killing the animal.
Apparent death is considered to be different from ‘freezing’ strategies used by animals such as deer, as freezing tends to happen as an early in an encounter and does not come with many of the other factors that give the impression of death.
It’s not always for Defence
Thanatosis, or ‘Tonic Immobility’ is not only used as a form of late-stage defence, but is also employed by some animals as a means to trick their way into a meal. In these cases, the animal enters the same comatose phase, attracting potential prey that then think they themselves are going to get a meal. When the predator comes to, they are able to grab themselves an easy meal.
9 Animals That Play Dead
Virginia Opossums are probably the most famous example of an animal that feigns death. They are also responsible for the saying ‘playing possum’ in reference to someone or thing pretending to be dead.
Their small size and limited physical defences make them an easy target for predators, particularly when they are young. So rather than trying to fight or flight, when an opossum is threatened, its body goes limp and its breathing appears to stop. It may also empty its bowels and discharge drool, with its tongue sticking out. If you poke it, the possum will usually not respond.
If they feel threatened but not overwhelmed, in the first instance they may just hiss and show their teeth to ward off competitors, mild threats or annoyances.
There are many different species and breed of ducks, and one thing they have in common is the ability to feign injury or death to confuse or distract predators. They don’t all do this however, but evidence suggests that it’s not a pointless exercise for those that do.
In one study, published in the journal ‘The American Midland Naturalist 94, no.1 (1975)‘, 50 wild ducks from 5 different breeds were exposed to a group of captive Red Foxes. All the ducks that displayed thanatosis when they were attacked has a better chance of survival. However foxes did learn, over time that despite appearances, a crippling wound was necessary to secure their meal.
When frightened, rabbits may freeze or “play dead” in hopes of avoiding capture or a potential predator. They may lie motionless with their eyes closed, or remain completely still in a crouched position. Both wild and domestic rabbits are known to take this a stage further though in late stage interactions with a perceived threat, and can both display tonic immobility.
Rabbits are more likely to display this behaviour when they feel trapped or claustrophobic. They may also do this when they feel neglected, but in most cases, it is their last line of defence against a threat. They will lay on their back or on their side and remain still and silent. They may also exhibit this behaviour if they are handled by a stranger, without care or attention. They are much more comfortable with all of their paws on the ground.
White Tipped Reef Sharks
Some shark species, such as the White Tipped Reef Sharks are known to enter a state of tonic immobility when they are disturbed or handled. In fact, inducing tonic immobility is often used as a strategy for handling by researchers.
When it comes to tagging sharks to observe movement, track and monitor, this is dangerous work. That risk can be mitigated by inducing tonic immobility. Researchers do this by stimulating the tiny sensory pores located on the snout of a shark, and then turning them on their back. It doesn’t just work on white tipped reef sharks, but on many species.
When they enter this state, the risk of injury to both shark and researcher is reduced significantly. Once they are released and flipped back over, they leave the subdued state. They normally come out of it within 15 minutes.
It’s not just researchers that can induce this state upon a shark, but Orcas have also been observed causing sharks to go into this state, even causing them to drown when doing so. According to the Shark Trust, there is evidence to suggest that they may use this as a method to hunt sharks.
Hognose snakes, commonly known as blow snakes, are known to put on a ‘theatrical performance’ when threatened. They will hiss and puff their bodies up, tilt their heads back in a cobra-like pose, and then they will roll over onto their backs and play dead. They may even let out a few loud squeaks while they are on their back. Similarly to a skunk, they may also let out a horrible ‘musk’ scent to deter a predator.
They are not the only snake to display thanatosis behaviour, but it is rare amongst them and they are perhaps the most dramatic.
Black Widow Spider
While the Black Widow Spider has a nasty bite, and can be particularly dangerous to humans, they do have many predators themselves. There are lots of insects, snakes and birds that are only to happy to try and make a meal out of them. While their bite might be effective, sometimes feigning death is the best, last chance option.
They are not aggressive spiders and will usually try to avoid any threat or conflict as a first response. In observations, the black widow was much more likely to roll up into a ball and feign death than it was to bite. While most species use tonic immobility as a last resort, with spiders that display the tactic, biting is usually their last resort, and they will feign death far more often. They do this by tightening up their legs into a ball and remaining still.
Some spiders may employ the tactic of thanatosis not only in the face of a threat, but as a tactic to attract a potential, cannibalistic female mate! One such example of a spider that does this is the Wolf Spider. Not only will a wolf spider feign death to attract a female in, but they will also use the tactic to avoid being attacked by the female after mating.
Female wolf spiders use thanatosis for different reasons than the male. The female will play dead to allow the male to deliver their sperm. This can be a bit confusing for male wolf spiders however, and they have been observed mating with females that are actually deceaced.
Green Sea Turtles
Some turtles will employ strategies to try and confuse predators. The green sea turtle, particularly baby turtles for example, have also been known to play dead in certain circumstances. The most dangerous time in a sea turtles life, is the time between emerging from their buried nest, and making their ‘do or die’ run into the safety of the sea. But they can also face many unintended risks, particularly from handling by researchers.
When baby turtles emerge and dash for the sea, they are incredibly energetic. They have saved up all of their energy reserves for this journey. Unfortunately, it is also the best time for researchers to grab and collect data on these animals. Particularly data on size, weight and useful information for conservation efforts. When picking them up, on the beach or even in the lab, they will struggle and wriggle. Dropping them can be particularly harmful at this tender age.
One paper in Chelonian Conservation And Biology suggests researchers can’t induce thanatosis by putting them on their backs like a shark, but they can induce it by placing the turtle into complete darkness, or by creating a sense of pressure similar to that they would feel in their egg in the nest. When these conditions are set, green sea turtles will enter a state of thanatosis allowing for safe observation.
Baby Brown Snakes
Another example of a snake that enters a state of thanatosis as a defence, are DeKay’s Brown Snakes (Storeria dekayi) – otherwise known as simply ‘brown snakes’. The behaviour is particularly common with baby brown snakes, that in their smaller and more vulnerable form are more likely to feel threatened.
They are known to enter tonic immobility, and maintain the apparent death pose, even when prodded or disturbed by a perceived threat. This includes when handled by an unfamiliar researcher with an unfamiliar scent.
The Yellowjacket Cichlid is an example of an animal that uses tonic immobility as a predatory tactic to attract prey. The fish has markings that make it look like a decaying fish to other aquatic life. With these markings, the fish will go into the paralyzed state of immobility and unsuspecting victims approach expecting an easy meal.
When the unsuspecting scavengers are close enough, even to the extent of nibbling on their skin, the yellowjacket regains consciousness and will turn the tables, devouring the tricked prey.
Is A Dog Playing Dead The Same Thing?
No, dogs generally do not enter a state of Thanatosis. When a dog plays dead, it is usually in response to a trigger or prompt by the owner. It is normally a conscious ‘performance’ to obtain reward or gratification for completion of a trick. They may repeat the behaviour as a form of avoidance in the presence of a task or object they don’t like, for instance to avoid bath time or the vacuum. But it’s not the same thing.